The U.S. Open Cup is an annual American soccer competition open to all United States Soccer Federation affiliated teams, from amateur adult club teams to the professional clubs of Major League Soccer (MLS). Each year, Major League Soccer, which has teams that play in both the United States and Canada, is allowed to enter eight of its U.S.-based teams in the tournament. The top six MLS teams from the previous season qualify automatically, and the remaining two spots are determined by preliminary qualification matches. The eight MLS entries begin play in the third round of the tournament.[2]In 2009, MLS expanded into the Seattle market adding a new team to the league, Seattle Sounders FC. As an expansion team, they had to play through the qualification matches before entering the tournament.[3] Likewise, D.C. United did not finish among the top six 2008 MLS teams, and therefore had to play through qualification rounds before entering the official tournament.[4]